Battery Type pros and cons

[Janice]

Hi What are the pros and cons of using recharable AA batteries or a 6V 4Ah lead acid battery charged by solar power to power a security light?

Janice

[Graham.]

For starters AA rechargeable are less than 0.3Ah but I suspect I am missing something here...

[Janice]

Hi it is just that I saw a security light for sale that uses 3 x AA Ni-Mh rechargeable batteries and leds and has a solar cell to recharge it and another one that uses a 6V 4Ah lead acid battery charged by solar power and a 10 watt halogen bulb so was wondering what would be the best in replacement of batteries and battery life? Janice

[meow2222]

I dont know what your question means. here's the battery info though:

?title=NiMH_batteryNT

[Dave Plowman (News)]

I'd say this is one use where a lead acid isn't a good idea - they don't like being run flat, unlike Ni-Cads. Unless it's a switched security light and you won't actually run the batteries low.

[tinnews]

All the rechargeable AA batteries I have are way more than 0.3Ah, even my oldish ones are 1800mAh which is 1.8Ah. I have lots of new ones which are 2700mAH, that's 2.7Ah. OK, it's less than 4Ah but I bet that 4 (or possibly 5) AA cells are smaller than the Lead Acid battery.

[Alan]

Surely it depends more on the light output from the LEDs vs the 10W halogen bulb for the application rather than the battery technology?

An expensive 3 or 5W LED is hardly bright enough for a security light. It may give enough light to illuminate something the size of a small patio just to the extent that you will be able to see what is there and not fall over it.

The OP suggested solar charging. I doubt that at this time of year the batteries would fully charge during the day and therefore you would be lucky to get more than an hour of light during the time when you wanted them most. Just consider those rechargeable garden lights that glow brightly during the summer nights but never get beyond a hardly visible glow this time of year.

[andrew]

I've one of those 500 candlepower spotlights with a gel batterry in it. As it needs a new battery is there a better repalcement than lead acid?

AJH

[Dave Liquorice]

Depends how long you want the light to run for... I have a similar thing from memory the bulb is 6v 55W and the battery a 4Ahr SLA. Get about 20 mins run time from it.

The largest AA NiMH are less than 3Ahr so even less run time and I'm not sure they would take all that kindly to a 10A load either. SLA is robust and simple, just a bit heavy.

[Dave Plowman (News)]

Crikey - hope it's a bright night if only 500 candle power. ;-)

With most of these things a complete new one costs less than a replacement battery. I'm not sure why there was a fashion for those lead acid handlamps. Ni-Cads etc are lighter and smaller. Perhaps something to do with voltage/capacity.

[The Medway Handyman]

I've got one of those B&D Lightsticks with 21 LED's. Great in a cupboard or under a sink, but nothing like bright enough for a security light.

[Dave Liquorice]

Voltage/capacity/size I suspect. D size NiCds are only 4Ahr, the 6v 4Ahr= SLA in my BFO lamp is smaller than 4 x D cells and is easier to connect/assemble being just a block.

Might be different now, I see CPC have industrial D size NiMH at 10Ahr a= t only =A39.83 each or 7Ahr at =A38.82 each (+ VAT). Consumer rarely get a= bove

3Ahr but I see a 11Ah "Powerex" twin pack for only =A316.45. Hum, perhap= s cost comes into in a bigger way a 6v 4Ahr SLA costs about a tenner...

[andrew]

Yes I meant 500k!

I've been given a couple and inherited this one, it's ok for about 30 seconds! As you say it's not worth replacing the battery.

Dave L says the batterry is 60 Whr to full dod, so maybe 30 Whr usable??

Anyway with the lead acid being 800 grams and Nimh rechargeable 2500 mA AA cells weighing 35 grams and 1.25V it looks like I only need 10 for the same performance and only half the weight or are my sums wrong.

AJH

[tinnews]

They *used* to be only 4Ah, you can now get at least 7Ah in a D size and probably more.

Ah, you've noticed that D cells have increased capacity now! :-)

As you say they are rather expensive, I suspect that the market for C and D cells is quite small nowadays, *everything* runs on AA and AAA.

[Dave Plowman (News)]

Sub C is the common one for power tools. If only they were so cheap outside the factory.